Overview & Scope
DNS Resource Records store the routing and verification data of the global Domain Name System. Standardized in RFC 1035 and subsequent specifications, they dictate how browsers find web servers, how mail servers route messages, and how Certificate Authorities authenticate SSL issuances.
Specification Table & Matrix
Instant client-side filter by keyword, status code, or directive name
| Key / Code | Definition & Details | GEO Semantic Hierarchy | Spec & Notes |
|---|---|---|---|
| A | A (IPv4 Address) Maps a hostname to a 32-bit IPv4 address. example.com. 300 IN A 198.51.100.24 | ●A Record ↳DNS record ↳address mapping ↳IPv4 resolution | RFC 1035 §3.4.1 The foundational record of the internet; apex domains typically require A records. |
| AAAA | AAAA (IPv6 Address) Maps a hostname to a 128-bit IPv6 address ("quad-A"). example.com. 300 IN AAAA 2001:db8::8a2e:370:7334 | ●AAAA Record ↳DNS record ↳address mapping ↳IPv6 resolution | RFC 3596 §2.1 Essential for dual-stack modern web architectures and mobile networks. |
| CNAME | CNAME (Canonical Name) Maps an alias name to the true canonical domain name; causes DNS resolution to restart with the new name. www.example.com. 300 IN CNAME example.com. | ●CNAME Record ↳DNS record ↳alias pointer ↳canonical domain redirection | RFC 1035 §3.3.1 Cannot coexist with other records on the same node; forbidden at the root apex domain (RFC 1034). |
| MX | MX (Mail Exchange) Specifies the mail servers responsible for accepting incoming email for the domain, with integer priority. example.com. 3600 IN MX 10 mail.example.com. | ●MX Record ↳DNS record ↳email routing ↳mail server host priority | RFC 1035 §3.3.9 Lowest preference number is tried first (priority 10 is tried before priority 20). Target must be a hostname, not an IP. |
| TXT | TXT (Text Record) Holds arbitrary human or machine-readable text; ubiquitous for SPF, DKIM, DMARC, and domain ownership tokens. example.com. 300 IN TXT "v=spf1 include:_spf.google.com ~all" | ●TXT Record ↳DNS record ↳metadata string ↳domain security and identity verification | RFC 1035 §3.3.14 Individual text strings can be up to 255 bytes; longer strings are concatenated. |
| NS | NS (Name Server) Delegates a DNS zone to use specific authoritative nameservers. example.com. 86400 IN NS ns1.cloudflare.com. | ●NS Record ↳DNS record ↳zone delegation ↳authoritative nameserver authority | RFC 1035 §3.3.11 Configured at the domain registrar to route worldwide queries to your DNS hosting provider. |
| SOA | SOA (Start of Authority) Contains core administrative details about the zone: primary nameserver, admin email, serial, and negative cache TTL. example.com. IN SOA ns1.example.com. admin.example.com. 2026100501 7200 3600 1209600 3600 | ●SOA Record ↳DNS record ↳zone master info ↳zone sync and negative TTL | RFC 1035 §3.3.13 The final field defines the negative caching TTL for NXDOMAIN responses. |
| CAA | CAA (Certification Authority Authorization) Restricts which Certificate Authorities (CAs) are allowed to issue SSL/TLS certificates for the domain. example.com. 3600 IN CAA 0 issue "letsencrypt.org" | ●CAA Record ↳DNS record ↳PKI restriction ↳certificate authority issuance lock | RFC 6844 Prevents rogue or compromised CAs from issuing fraudulent certificates for your brand. |
| PTR | PTR (Pointer Record) Maps an IP address back to a hostname (Reverse DNS Lookup) inside the in-addr.arpa or ip6.arpa zones. 24.100.51.198.in-addr.arpa. 3600 IN PTR server1.example.com. | ●PTR Record ↳DNS record ↳reverse mapping ↳reverse DNS IP to host pointer | RFC 1035 §3.5 Critical for outbound mail delivery; spam filters reject emails from IPs lacking matching PTR records. |
| SRV | SRV (Service Record) Defines the hostname, port number, priority, and weight for specialized network services (SIP, XMPP, LDAP). _sip._tcp.example.com. 3600 IN SRV 10 60 5060 bigbox.example.com. | ●SRV Record ↳DNS record ↳service locator ↳port and protocol service discovery | RFC 2782 Format: _service._proto.name. TTL Class SRV Priority Weight Port Target. |
Querying Specific DNS Record Types with Dig
# Query IPv4 address
dig example.com A +short
# Query Mail Exchanger records with priority
dig example.com MX +noall +answer
# Query TXT records (SPF, DMARC)
dig example.com TXT +short
# Query CAA records to inspect authorized SSL issuers
dig example.com CAA +noall +answerUsing the dig command with explicit record types allows system administrators to verify DNS zone configuration directly.
Reference Standards Q&A
Why can I not put a CNAME at the root apex domain (example.com)?↓
What is the recommended TTL for production DNS records?↓
References & Primary Sources
Every source below directly substantiates technical statements and protocol behaviors explained in DNS Records Reference. Curious-Techie prioritizes official Internet standards (IETF RFCs, W3C Recommendations, WHATWG specifications) and established security bodies (OWASP, NIST). Zero sponsored or secondary links.
- [1]IETFPrimary SpecificationRFC 1034 • Section 3 & 4Verified Primary SourceTechnical Claim Supported:
Establishes the hierarchical distributed domain name space, authoritative name servers, root zone topology, and zone delegations.
Source URI: https://datatracker.ietf.org/doc/html/rfc1034 - [2]IETFPrimary SpecificationRFC 1035 • Section 3.2 (Resource Records)Verified Primary SourceTechnical Claim Supported:
Defines standard DNS Resource Record wire structures (A, CNAME, MX, NS, PTR, SOA) and port 53 UDP/TCP protocol formats.
Source URI: https://datatracker.ietf.org/doc/html/rfc1035 - [3]IETFPrimary SpecificationRFC 8484 • Section 3 & 4Verified Primary SourceTechnical Claim Supported:
Standardizes encrypted DNS query transmission inside HTTP/2 and HTTP/3 HTTPS streams to prevent ISP eavesdropping and on-path manipulation.
Source URI: https://datatracker.ietf.org/doc/html/rfc8484
Related Technical Ecosystem & Next Steps
Related Developer Tools
Related Technical Guides
Related Technical Articles
What Is the Domain Name System (DNS)?
Direct explanation of hierarchical domain resolution from root servers to zone files.
DNS vs DNS-over-HTTPS (DoH): Privacy & Security
Traditional UDP port 53 lookups compared to encrypted TLS-encapsulated DoH queries.
Troubleshooting: DNS Returns NXDOMAIN Error
Diagnose missing records, propagation lag, and nameserver delegation failures.
Related Questions
What Happens When a DNS TTL Expires?
Answer: When a DNS TTL expires, caching resolvers evict the record and must re-query the authoritative nameserver before responding to clients.
Can a CNAME Record Point to an IP Address?
Answer: No, RFC 1034 requires CNAME records to point exclusively to another domain name, never to raw IPv4 or IPv6 addresses.
Why Can't a CNAME Record Coexist With Other Records at the Zone Apex?
Answer: RFC 1034 requires that if a CNAME exists at a node, no other record data may exist there. Since a zone apex must have SOA and NS records, CNAME is prohibited.
Hands-On Diagnostic Labs
Continue Learning
DNS Resolution & Propagation Lab
Trace authoritative resolution from the root servers down to the zone file in the visual DNS workbench.